The use of segmented couplings with fastening means to achieve mechanical couplings for joining and sealing the ends of pipes has been widely utilized by the industry because of the convenience of installing such devices. Such segmented couplings have been extensively patented since 1960 and have been used, for example in the installation of overhead sprinkling systems in fire prevention equipment. The patents describe many variations on the basic segmented coupling and it is just in the last few years that this industry has become sophisticated to the extent that intricate designs have played a major role in the utility of the coupling devices as they are being commercially used today.
One such coupling device is disclosed in U.S. Pat. No. 3,054,629 issued Sept. 18, 1962, and includes a pair of arcuate coupling segments which span and embrace the adjacent ends of a pair of pipes which compress a sealing gasket into engagement with the external periphery at the end of the pipes. The coupling segments have inwardly extending engagement means for engagement within grooves in the adjacent pipe ends, and have radially extending pads at their ends which receive bolts employed for the tightening down of the coupling. It should also be noted, that the bolts tighten in the vertical axis of the coupling, at both ends of the coupling, and not along the longitudinal axis of the pipe, thus not giving any longitudinal draw to the coupling.
Typically, when the segments are secured together they extend in a continuous ring about the circumference of the pipe ends and substantially immoblize the pipe ends and attempt to eliminate gaps between the segments and the pipes. On the other hand, differences in the diameter of stock pipe of the same nominal diameter result in a less than optimal immobilization of the pipe ends, and gaps which permit extrusion of the gasket contained therein, are formed. Problems also arise due to differences in the depth of the groove on the pipe ends or the height of the beads placed thereon for secure coupling. If the pipes are undersized in diameter, or the groove diameter is too small, then the bolting pads may be brought into face engagement with each other, but the desired immobilizing clamping force on the pipe ends may not be obtained owing to the ill fit of the device or the lack of longitudinal draw. If the pipes are oversized in diameter, or the groove diameter is too large, then the bolting pads may not be brought into essential face engagement with each other and may leave a gap between the bolting pads through which the gasket can rupture and extrude. To overcome these problems, closely spaced supports or hangers have been employed to eliminate undesirable flexure at the joint, or extrusion shields have been provided to support the gaskets in the area of the gap between the bolting pads.
Gibb, et al. in U.S. Pat. No. 4,471,979, teaches that thin-walled piping which is inherently capable of moving out-of-round under compressive stresses produced by the tightening down of the coupling, can be handled by deliberate formation of the coupling segments to have them subtend an angle of less than 180 degrees at their end faces, to permit the centers of curvature of the respective coupling segments to move beyond and to the opposite side of the diametral plane of the coupling. This selective deformation of the pipe ends by that coupling provides for rigid clamping of the coupling onto the pipe ends without regard to whether the pipes are oversized or undersized within the range of manufacturing tolerances. It should be noted that this reference also deals with fastening means which are bolts which tighten in the vertical axis of the coupling at both ends of the coupling, and not along the longitudinal axis of the pipe thus, as mentioned above, it does not give any longitudinal draw to the coupling. This construction has little utility for use with conventional pipe that is not readily deformable by a coupling, and does not entirely eliminate the need for extrusion shields in those circumstances where the bolting pads do not reach total end face engagement with each other.
Gibb, in a later patent. U.S. Pat. No. 3,756,629, issued Sept. 4, 1973, teaches a stud system of joining pipe and the couplings used for that joining. In this reference, radially projecting studs are secured around the outer circumference of pipes near the pipe ends by arc stud welding. The couplings may be formed in two or more arcuate parts which mate to form a complete ring.
Much later, in U.S. Pat. No. 4,522,434, issued June 11, 1985. Webb teaches a segmented coupling for use in a high-pressure piping system having cast multiple keys in their as-cast condition, which are for reception within corresponding plural or multiple grooves in pipe ends. Crushing of the operative faces of the keys and cold working of the faces of the pipe grooves in engagement therewith provide for equalization of the axial loading imposed on the respective keys. The draw down devices of that invention are all designed to draw in the same direction, none of which draw in the longitudinal axis of the pipe.
Kunsman, in U.S. Pat. No. 4,56l,678, issued Dec. 31, 1985, teaches a coupling similar to the Webb device, but in addition teaches a tool that can be used with lugs on the device to give easy and secure placement of the coupling on the pipe. Kunsman, except for the arrangement of the tool lugs and the like on the coupling, do not add to the teaching of the Webb disclosure. The same can be stated about the teaching found in U.S. Pat. No. 4,601,495, issued on July 22, 1986 to Webb in that the same essential coupling as described in the Webb '434 patent and the Kunsman patent is described therein.
DeRaymond et al in U.S. Pat. No. 4,702,495 teaches a hingeable segmented pipe coupling which has as its main feature, a specific design for the hinged portion of the coupling. It is noted that the coupling has only vertical fastening means and that there is no draw along the longitudinal axis of the pipe.
Finally, U.S. Pat. Nos. 4,611,839 and 4,639,020, issued on Sept. 16, 1986 and Jan. 27, 1987, respectively, are related and describe a self-adjusting pipe clamp and coupling which is segmented and which includes coupling segments having bolting pads at their ends, the ends of the coupling segments include inclined end faces for cooperation with corresponding inclined end faces of an adjacent coupling segment to produce self-adjustment of the coupling and rigid clamping of the pipe ends upon tightening down of the coupling. It should be noted that both of these references teach exactly the same coupling and that these are the only two references that teach such a concept, and that that teaching deals mainly with the inclined end faces of the coupling segments, and that the references teach several types of bolting arrangements, with the exception that they do not teach a bolting arrangement in which the bolts are drawn along the longitudinal axis of the pipe when a separate end face is constructed on the coupling segment to prevent rotational twist and pipe gaggage, nor do they teach the use of end faces that are essentially planar in the diametral X-Z plane and parallel to the Z axis of the pipe coupling. For example, in FIG. 26, therein, there is shown a vertical bolting arrangement which contains a pin having its longitudinal axis parallel with the longitudinal axis of the pipe but the pin does not have a drawing action along the longitudinal axis of the pipe, and further, it only has the function of holding the parts of the hinge together and allowing rotation of the hinged parts around its outer circumference.
The '839 and 020 patents each teach the use of inclined faces on the bolt lugs to achieve a movement of the arcuate segments such that they are intended to reduce the internal circumference of the coupling as it is tightened and to give positive clamping on the pipe ends. The arcuate segments having angled faces as taught in the '839 and '020 patents however have significant disadvantages when in actual use. If those skilled in the art study those references carefully, they will note at least two significant differences between the prior art couplings and those of the instant invention. The prior art segments do not have end faces on the couplings that are planar in the diametral X-Z plane (defined infra) and which extend parallel to the Z axis of the pipe coupling; the prior art segments do not have oblique angled faces on the bolt lugs which draw to the inside and which allow a draw of the segment along the parallel axis of the pipe when it is situated in the coupling and, in one preferred embodiment of the instant invention, the prior art does not teach the use of lugs to give a direct draw along the long axis of the pipe when it is positioned in the coupling. Thus, the prior art, oblique angled segments all have angles which cause the coupling to be drawn to the outside in directions not exactly parallel to the long axis of the pipe. Thus, when the arcuate segments of the prior art are put together to form a coupling around a pipe and then tightened, the beveled faces of the segments cause rotational twist which causes forces on the pipe ends which cause the pipe ends to separate. This is true because the prior art couplings do not have the end faces that are planar in the diametral X-Z plane and parallel to the Z axis of the pipe coupling. These faces, as disclosed in the instant invention, will not allow the coupling segments of the instant invention to exceed a predetermined reduction of the internal circumference of the coupling when it is tightened and thus, the rotational twist is prevented. The couplings of the instant invention will couple pipe ends together to give a coupling which has zero flex and absolutely no gappage occurs between the pipe ends, and further, couplings of the instant invention, eventhough they are lighter in weight and construction, have greater strength than those couplings of the prior art, especially those that are disclosed in the '839 and '020 patent disclosures.
Thus, it does not appear that the instant invention has been disclosed in the prior art and the advantages of the instant invention are not therefore obvious to those skilled in the art.